The present invention relates to an automatic repeater station and, more particularly, to an automatic repeater station for serving at least eight (8) channels each having separate receivers and transmitters and all of which are devoid of any tunable filters.
Automatic repeater stations are commonly referred to as radio relay systems, or simply a radio relay, and may operate within the UHF frequency band of between 225-440 MHz commonly used in the military. The propagation of radio signals in the military UHF band (225-400 MHZ) is normally limited to the line of sight between two communicators. However, an airborne radio relay system, by means of its obtainable height, can increase the line of sight and hence increase the propagation range between communicators. The frequencies at which these signals are transmitted and received are grouped into channels, with particular channels being assigned to individual users.
At the present time, a maximum of only three channels can be relayed simultaneously in any one application. One of the primary reasons for this limitation is because a standard transceiver is used to perform both the receiving and transmitting functions of the relay system. The standard transceiver comprises a transmitter and a receiver both in one housing sharing a common input/output antenna connector and possibly other components. Because a transceiver cannot transmit and receive simultaneously, two transceivers must be used to service one relay channel and, therefore, six transceivers are needed to service three relay channels. Also, since a radio relay must receive and transmit simultaneously, two different frequencies are used and are commonly referred to as F1 and F2. The primary reason for the two different frequencies is to eliminate any self jamming therebetween. The use of one frequency F1 for receiving and a different frequency F2 for transmitting further increases the disadvantages of using a transceiver. In particular, one transceiver selected to operate at a particular frequency cannot be used for both transmitting and receiving.
Although it is desired that a relay system be provided having at least an eight channel capability, the use of transceivers for such a system would yield an oversized and overweight device both of which characteristics are detrimental to military applications and even to civilian applications. For example, a three channel relay that is now mounted in a pod, or streamline compartment of an aircraft, may have a total weight, including the pod, of about 720 pounds. It is desired that a relay system having an eight channel capability be provided, but without the use of transceivers so as to reduce the size and weight of the system.
In addition to relatively heavy transceivers, an additional relatively heavy device is an electronically tunable filter that is presently used in relay systems. It is desired that means be provided to eliminate the need of electronic tunable filters so as to further reduce the size and weight of the relay system.